Progressive heating cartridge



-D. FERRELL PROGRES S IVE HEATING CARTRIDGE April 26, 1932.

Filed Jan. 18, 1929 IIIIII.'

IIII Igm Inl - plied to blasting Patented Apr. 26V, 1932 DENT FERRELL,

OF HARRISBURG, ILLINOIS, ASSIGNOR TO SAFETY MINING COMPANY,

OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS PROGRESSIVE HEATING-CARTRIDGE Application led January 18, 1929, Serial No. 333,400, and inGreat Britain October 5, 1928;

This invention relates to improvements in the method of dischargingcartridges, such as for example, blasting cartridges, and to means forpracticing the improved discharging method. e

The invention is herein illustrated as apcartridges of the typecomprising a casing having carbon dioxide contained therein underpressure together with suitable means for raising the temperature of thecarbon dioxideto or slightly above its critical temperature, whereby thecartridge is discharged by rupturing one wall thereofgiving vent to theexpanding gas which acts to bring down a Wall of coal, rock, or othermaterial in accordance with the use to which the cartridge is put. Thistype of cartridge is fully described and claimed in the copendingapplication, Serial No. 169,441, filed February 1:2, 1927, by theapplicant and Arthur W. Helmholtz as joint it lventors, and itrepresents the type of device to which the present ninvention relatesand on which it is an improvement.

One danger which has been present in blasting operations, such as mineblasting operations, is that of explosions occurring in the rooms ofthemines caused by explosive gases which sometimes accumulate in explosivevolumes, being set off or ignited by sparks issuing from the cartridgeduring blasting discharge. This danger is for the most part entirelyeliminated in blasting operations where carbon dioxide or similarlblasting mediums are employed due to the inherent characteristics ofthis type of medium. The blasting force of carbon dioxide is derivedfrom its power of vaporization and expansion upon being heated to orslightly above its critical temperature when in liquid form and underpressure, which action is entirely diterent from that of ordinaryexplosive substances, such as dynamite for instance. Dynamite or similarsubstances produce exothermic chemical reactions upon explosion whichgive oft" a tremendous amount of heat and the gases produced thereby areactually products of combustion. By the use of a gas, such as carbondioxide, which is merely vaporized and expanded without chemical change,it becomes obvious that blasting operations practiced with carbondioxide or similar substances are very much safer than those practicedwith other blasting materials. A

As above mentioned in carbon dioxide cartridges it is necessary toprovide some means for raising the temperature of the carbon dioxidemedium to or slightly above its critical temperature and it has beenfound convenient in practice to do this by igniting a substance whichwill evolve the proper amount of heat while maintaining the substance inproper heat transferring relationship relative to the carbon dioxidemedium.

It, therefore, becomes desirable to provide a heating element which maybe initially ignited by any suitable means such as by an `electricalcurrent, which means is the most convenient and thus the mostpreferable, which will develop exactly the amount of heat necessary fordischarging the cartridge, but will not continue its igniting or burningaction after the cartridge has been discharged. Also a heating elementwhich is entirely free from all possibility of emitting sparks, orignited or igniting material such as might be presented in contact withexplosive gases in the mine resulting in an explosion in the mine roomcausing damage to property and injury to the Workers.

It is, therefore, an object of this invention to provide a method andmeans for discharging cartridges of the type described in the copendingapplication above referred to which will be entirely free of theforegoing dangers.

Other objections not enumerated will appear las theV descriptionproceeds.

The invention accordingly proceeds upon the principle of developing theheat necessary to raise the blasting medium to or above its criticaltemperature, progressively, that is to say, little at a time until thetotal required heat is reached. Although this involves some time elementbetween the instant of initial ignition and resulting discharge, it mustbe borne in mind that the entire heating action is extremely rapid andin practice is found to occur within the limits of approximatelyone-twentieth of a second. This progressive heating when employed withme- I diums, such as carbon dioxide, acts to assure a high de ree ofsafety, as it is found that the cartrige will discharge immedlatel uponreaching the critical .temperature wit further ignition of the heatingmaterial autowill be required, but due to slight variation tion willstart from one this cannot always be done, and, therefore, a

slight excess should be provided so as to assure discharge in everyinstance. As above explained, w1th the present progressive heatingmethod the presence of such excess does not present any degree ofdanger, as continued ignition of this excess material is completelychecked, the igniting action being extinguished and the particles ofheating Inaterial violently discharged and agitated as minute particlessuspen heat absorbing medium.

The heating element may be actually constructed in shape relativelylongwith a relatively small cross-sectional area, and provided with means,such as a fusing element, match head, or squib, for initiating theigniting action, located in a predetermined local volume thereof, sothat the igniting acpredetermined point and continue of its own accordprogressively throughout the entire length of the element. Due to therelatively small cross-sectional area of the element, the volume ofheating material burning or undergoing igntion at any one instant, isrelatively small and coned in the expanding sequently the heat requiredfor discharge is progressively developed as the heating element burns.

It is apparent that the advantages of this invention may be realizedwith elements having a single fusing element or squib located I actionto give the in one end thereof, or located at any other predeterminedpoint throughout the length of the elementprovided only that there issufficient of the heating material located remote'- ly from the point ofinitiating the igniting progressive heat developing action. Thus, lthefusing element or squib may be located centrally or any other desiredpoint. It is also apparent that more than one 'fusing element or-squibmay be employed, as

Y the progressive heating action can be' proinitially ignited and bycaus- `heating elements shown in views siml vcartridge construction willnot be duced even though the igniting 'action 'be' K is not to beconsidered as limiting the invention in any particular. The scope of theinvention will be determinable from an under- 4 standing of the presentdisclosure as one embodiment thereof, and with an appreciation of theadvantages produced in the particular embodiment illustrated. Byreferring to the drawings- Flgure 1 is a cross-sectionalview in sideelevation'of a cartridge-equipped with a heating element constructed inaccordance with this invention; Figure 2 is a cross-sectional view of aheating element constructed in accordance with this invention; and iFigures 3, 4 and 5 are modified ty es of Ilar to Figure 2. Referring tothe drawings, itwill be noted that the present invention is disclosed asembodied in a cartridge comprising a casing 10 having a ru turabledisk11 and directing cap 12 at the. ischarge end and means 13 forestablishing an electrical connection for the heating element, and forintroducing the blasting medium into the cavity 14. vTh'e'f described-5'in detail as it is substantially the same as disinserted in theposition' shown in Figure 1 with its electrical connection 16 at one endin contact with the rupturable disk 11 and the electrical connection 17at its opposite end inl contact with the plate 18 constituting the otherterminal for theelectrical circuit.

Referring to Figures 2 to 5 inclusive, it will be noted that the heatingelement comprises a tube 19 which may be of any suitable material, suchas for instance, wax paper, which is found to serve well in practice,having. closing plugs 20 at its two ends formed of any suitablematerial, such as for instance, cork. The heating mixture 20,iscontainedV within the tube 19 and a conducting wire 21 terminating atone endas at 16, and at the other end as at 17 by passing between thecorks 20 and the tube 19 is lalso passed through the tube. VThe wireterminals are preferably in the form of a small coil spring so as toassure more perfect contact.

The mixture 20 may be'of any suitable ma- I terial, such as forinstance, a mixture of sodium chlorate, aluminum, and wood char'- coal,all mixed together in suitable portions,

closed in the copending application referred...

lll

such as the following, which are found to produce a good mixture inpractice:

Per cent Sodium chlorate i Aluminum 13 Wood charcoal 6 The electricalconnection 2l has connected in its length a match head or squib 22embedded in the material so that upon the passage of electrical currentthrough the match head or squib an ignition of the material is startedlocally in the area immediately surrounding the match head or squib. Theconducting Wire may be of any suitable material, such as of soft ironWire, copper, or nichrome. In the form shown in Figure 3, a diminishedamount of ignition material is provided, the remaining portion of thetube being lled with a suitable inert material 23, such as fullersearth, or like substance. In Figure 4, a slightly diderent form of matchhead or squib is shown as at 24 serving, however, to initiate theignition in a local area the same as described above. In Figure 5, afusible Wire 25 made of copper or like suitable material is provided forinitiating the ignition whereby the material is ignited throughout alocal area immediately surrounding'the wire 25. It is preferable toprovide the tubes 19 of Water proof paper or of any material Which willcontain the material and maintain a predetermined form according to thecontour desired.

In operation, it will be appreciated that as an electrical current ispassed through the heating element by means of the cartridge beingproperly connected to a suitable exploder, such as for example, amagneto or current and switch line, the material contained within theheating element is ignited throughout its area immediately around thematch head or squib so that the material once ignited causes progressiveignition throughout the length of the heating element, further, thatthis ignition will continue until the proper heat is developed withinthe container for bringing the temperature of the medium to or slightlyabovev its critical temperature or to the discharging temperature. Alsoat this time, further ignition is intermediately terminated as thedischarging of the cartridge causes a large and rapid heat absorptiondue t'o the evaporation and gas liberation together with a violentagitation and division of the heating material into minute particles inwhich form continued ignition is immediately extinguished. `With thisunderstanding of the applicants improved method and means, it will beappreciated that the.present invention provides a means for producingexactly the required amount. o

heat Jfor discharging the cartridge and for automaticallyterminating'the heat generat ing ignition action at the moment theneces.

sary heat is arrived at.

explosion and consequently elimination of all the dangers above referredto which are undesirable in mine blasting or otherblasting operations.

The present disclosure and description is given merely by Way ofillustration as one form of the present invention and is obvious thatvarious modiiications may be resorted to Without departing from thespirit of the invention, the scope of which is set forth in the appendedclaims.

I claim:

1. In a device of the character described, a relativelylong containerhaving a relatively small cross-sectional area, said container having amixture therein of sodium chlorate,

aluminum and carbon and means for initiating ignition thereof throughouta local area' of its volume.

2. In a device of the character described, a relatively long containerhaving a relativelyl small cross-sectional area, said container having amixture therein of sodium chlorate, substantially 81%; aluminum,substantially 13%; and carbon, substantially 6%; and means forinitiating ignition thereof throughouta local area of its volume.

3. The method of developing heat in gas charged blasting cartridgeswhich consists in providing a quantity of combustible heat producingmaterial, igniting the material at a given point and causing progressivecombustion in relatively small increments until the amount of heatrequired for discharge of the cartridge has been thus progressivelydeveloped, whereupon combustion ceases.

4. The method of developing heat in blasting cartridges charged withhighly compressed carbondioxide and provided with pressure responsivedischarge means, consisting in providing a combustible materialproportional in quantity to the charge of carbon dioxide, igniting thematerial at a given point and causing progressive combustion of thematerial in relatively small increments until the amount of heatrequired for discharge has been thus progressively developed, whereuponthe discharge causes cease.

' 5. A heater .unit for use in gas charged blasting cartridges,comprising a relatively long body of combustible material of relativelysmall cross sectional area and means for initiating ignition of saidmaterial throughout a small area, all for the purpose of developing`therequired amount of heat in a continuously progressive manner andavoiding an excess of heat by reason of the autothecombustion tol maticextinguishment of the heater unit ims mediately upon discharge of thecartridge.

6. A heater unit for use in gas charged blasting cartridges, comprisingan 'elongated tubeof relatively small cross sectlonal areaJ containing areadily ignitible heat producing material, said mate said tube 54 o'fsaid material lengthwise'of said tube with conse the point at whichSlgned at Mario January, 1929.

quent progressive heat development to discharge occurs. n, Illinois,this 47th day of DENT FERRELL.

